1. Field of the Invention
The present invention relates to a headphone and more particularly to a headphone provided with a housing containing a drive unit and adapted to reproduce sound by means of the drive unit.
2. Description of the Related Art
The headphone is used for personally enjoying reproduced sound of music and the like. Such headphones are generally divided into two types: open-air type and closed type.
The headphone of the open-air type has a permeable ear pad and has the housing containing the drive unit and provided with a through hole formed therein. Therefore, when a listener wears the headphone to listen to a reproduced sound, the sound produced within the housing easily leaks out and also sound from the outside can be heard by the listener. While the headphone of the open-air type has acoustic transmissibility between inside and outside the housing and, hence, it allows the sound to be heard as a natural sound, the sound is greatly attenuated in the low-pitched sound range below f0 (the lowest resonance frequency) and tends to lack the low-pitched sound component.
On the other hand, the closed type headphone has the housing containing the drive unit closed and has the ear pad keeping sound from leaking out. Although a rich sound characteristic in the low-pitched sound range can be obtained from the closed type, it is difficult to obtain a natural sound from this type.